1. Field of the Invention
The present invention relates to packet networks and, more specifically but not exclusively, to time synchronization across packet networks.
2. Description of the Related Art
This section introduces aspects that may help facilitate a better understanding of the invention. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is prior art or what is not prior art.
Time synchronization deals with the actual and precise distribution of a timescale in a network that enables nodes in the network to be synchronous. As used herein, the terms “time synchronization” and “synchronization” are assumed to be synonymous. Time synchronization of nodes across a packet network has traditionally been accomplished using a packet-layer protocol that relies on the arrival times of timestamped packets to achieve time synchronization. Unfortunately, packet-layer protocols have their limitations and costs.
There has been recent work on schemes that combine a packet-layer protocol with a physical-layer protocol to achieve time synchronization. Physical-layer protocols rely on the existence of bit transitions to achieve syntonization (i.e., coordinating frequency between different nodes). Such schemes involve continuous implementation of both the packet-layer protocol and the physical-layer protocol, with the packet-layer protocol updating the time based on sync messages that arrive at least once every second, and the physical-layer protocol continuously updating frequency based on bit transitions.